The present invention relates to a method and an apparatus for sensing the presence of arc discharge in an arc discharging circuit.
In order to determine the welding quality in an arc welding device, there is a known method for sensing its welding current. The method is convenient as the welding current is sensed easily by providing a transformer (current transformer) in an electric current feeding line. However, it is sometimes activated erroneously by inductive noise from the outside and there also is a situation where a large electric current flows without arc discharge because of a base material coming in contact with a work-piece and it is erroneously sensed as arc discharge.
For the purpose of dealing with such errors, there is a known method for sensing arc light to determine the quality of arc discharge. It can be said that as a method for sensing the presence of arc discharge, this method is better than the method in which an electric current is sensed.
However, even in the method for sensing arc light, the apparatus may be activated mistakenly by light in a surrounding area or arc light of another welding operation which is carried on at close quarters. This problem can be solved by shading light in the surrounding area, however, to structure such shading is difficult since it affects arc discharge and is expensive.
Accordingly, the present invention aims to provide a method and an apparatus that can sense the presence of arc discharge easily and reliably.